Mossy fiber sprouting in the dentate gyrus in a newly developed epileptic mutant, Ihara epileptic rat

We examined the correlation between seizure activity and development of mossy fiber sprouting in the hippocampal formation using Timm staining in a newly developed Ihara epileptic rat (IER). The sprouting of mossy fibers were clearly shown in the inner molecular portion of the dentate gyrus and in the stratum oriens of CA3 pyramidal cell layer with repeated seizures. A positive correlation between the frequency of generalized tonic and clonic convulsions and the Timm staining score in molecular layer of dentate gyrus was revealed. Sprouting of mossy fiber in IER seems to be linked with seizure activities resulting from epileptic bursts, not to the genetic mutation.